Sinoatrial malfusion presenting with caudal position of right atrial appendage.

A 5-year-old boy underwent surgery at our institution for closure of an ostium secundum atrial septal defect. Median sternotomy revealed that the right atrial appendage lay at the acute margin of the heart. Atriotomy revealed that the crista terminalis was also displaced clockwise, extending from the left of the superior vena caval orifice anteriorly along the interatrial septum, to the left border of the inferior vena cava; the musculi pectinati radiated forward and to the right. This highly unusual anomaly is likely due to clockwise rotation of the atrial portion in relation to the normally positioned sinus venarum portion of the atrium, which resulted in sinoatrial malfusion.